McCune-Albright syndrome (MAS), a rare multisystem disorder caused by GNAS1 gene mutation is characterized by polyostotic fibrous dysplasia of bone (FD), endocrine disorders and caf-au-lait skin hyperpigmentation. FD affects craniofacial bones including the jaws in 90% of cases. FD/MAS patients are also associated with dental disorders that include tooth rotation, tooth displacement, missing teeth, enamel hypoplasia, enamel hypomineralization, abnormally large pulp chamber, retained deciduous teeth, attrition and severe malocclusion Dental management of FD/MAS is medically compromised by endocrine disorders and handicapping bone pain. Furthermore, bisphosphonates often used to control FD and associated bone pain poses a risk for jaw bone necrosis. Earlier subjective reports indicate dental surgery could exacerbate jaw FD lesions but there is still limited qualitative data on dental outcomes and effectiveness of dental treatments i maxillo-mandibular FD/MAS patients. Our collaborative group has access to the largest well-described and well-characterized cohort of 140 FD/MAS patients enrolled in an ongoing NIDCR/NIH natural history study of MAS. This patient population represents an appropriate cohort for intramural-extramural collaborative research that will assess outcomes of dental treatment in FD/MAS. Our objective is to determine the outcomes of dental therapies on maxillo-mandibular FD lesions in MAS patients and also the impact of FD on the prognosis of dental therapies. Using a combination of retrospective and prospective longitudinal case-cohort analysis we will assess in Aim 1 the outcomes and effectiveness of endodontic and orthodontic therapies in FD/MAS patients with maxillo-mandibular FD. In Aim 2, we will determine whether or not dental surgery within FD is associated with delayed healing, bone necrosis and exacerbation of FD disease burden. New knowledge gained from this unique patient population with a rare disease will provide evidence-based data to support 'best clinical practice' guidelines for dental care that will improve quality of life of FD/MAS patients.